Sound Devices will mention checking the menu option for the 722 Firewire port - set for computer connection, or to run hard drives. However, I have 2 722's at work, and there are just some combinations of computer/OS that will not work reliably, and SD generally can't help. I have one old Mac Pro that worked fine on OS10.5.x, but refused to mount reliably with OS10.6.8. A MacbookPro with OS10.6.8 works just fine. I've actually given up on Firewire transfers with 722s, and always record to HD and CF card, and just transfer with the CF cards.
While FW was supposed to be designed to be hot swappable, there have apparently been enough cases of burning out some FW ports that many manufacturers recommend power down before altering a FW connection.